JP2009248763A - Manufacturing method of aluminum wheel, and aluminum wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an aluminum wheel having high corrosion resistance and high adhesiveness to a coating film; and the aluminum wheel. <P>SOLUTION: The manufacturing method of the aluminum wheel comprises a release agent removing process removing a release agent from the surface of the aluminum wheel made by molding an aluminum base material or an aluminum alloy base material with a physical means and/or chemical means, and a pickling process cleaning with an acid solution containing &ge;0.5 g/L to &le;10 g/L metal ions and &ge;10 g/L to &le;100 g/L nitric acid. The metal ions in the pickling process includes at least one kind of metal ions selected from a group consisting of Fe<SP>3+</SP>ion, Ni<SP>2+</SP>ion, Co<SP>2+</SP>ion, Mo<SP>6+</SP>ion, and Ce<SP>4+</SP>ion. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an aluminum wheel manufacturing method and an aluminum wheel, and more particularly to an aluminum wheel manufacturing method having high corrosion resistance and high adhesion to a coating film, and an aluminum wheel.

  Since the aluminum base material and the aluminum alloy base material are brilliant and light in weight, the use of these properties is expanding in various fields. For example, automobile wheels are mainly made of iron. However, demand for aluminum wheels made of an aluminum alloy base material has been increasing since automobiles are required to have higher grades and lighter weight.

  When an aluminum base material or an aluminum alloy base material (hereinafter collectively referred to as an “aluminum-based base material”) is cast and / or forged into an aluminum wheel, the surface of the mold is used for casting and / or forging. An agent, an aluminum oxide film formed during casting and / or forging, dirt, oil, and the like (hereinafter collectively referred to as “impurities”) are adhered.

  Moreover, these impurities become a factor which reduces the adhesiveness of the coating film to an aluminum wheel. Therefore, before coating the aluminum wheel, it is necessary to remove the impurities by performing a pretreatment for coating.

  Furthermore, since the aluminum base material has low corrosion resistance, if there is a scratch on the surface of the aluminum wheel, thread rust is generated or an oxide film is formed on the surface. Therefore, it is necessary to perform a treatment for improving the corrosion resistance on the surface of the aluminum wheel.

  In order to remove the impurities, conventionally, processing by physical means such as shot blasting has been performed on an aluminum wheel obtained by casting and / or forging an aluminum base material. Further, chemical etching treatment using an alkali treatment liquid or an acid treatment liquid is performed on the surface of the aluminum wheel as an alternative or in combination with a treatment by physical means.

  At this time, for example, shot blasting is usually performed with metal (eg, iron, stainless steel, etc.) shot grains. Therefore, iron in the shot grains remains on the surface of the aluminum wheel after shot blasting.

  Thus, the iron remaining on the surface of the aluminum wheel becomes a factor that inhibits the adhesion between the surface of the aluminum wheel and the coating film. In addition, moisture in the atmosphere permeates the coating film, reacts with iron and aluminum as a base material, and causes a decrease in corrosion resistance.

  Therefore, in recent years, techniques have been developed to remove metal remaining on the surface of the aluminum wheel after shot blasting, improve the adhesion of the coating film to the aluminum wheel, and improve the corrosion resistance of the painted aluminum wheel.

  For example, in Patent Document 1, an aluminum wheel that has been molded and taken out from a formwork, and surface treated by shot blasting and cutting is subjected to degreasing, water washing, pickling treatment, water washing, chemical conversion treatment, water washing, and post-treatment. A method is described in which coating is performed on the aluminum wheel after sequentially performing and drying.

  In Patent Document 1, it is described that an acid solution having a pH of 0.6 to 2.0 containing ferric ions 0.2 to 0.4 g / L and sulfuric acid is used for the pickling treatment.

  In addition, in the chemical conversion treatment, zirconium ions or titanium ions 0.01 to 0.125 g / L, phosphate ions 0.01 to 1.0 g / L, and fluorine ions 0.01 to 0.5 g / L. It is described that an acidic film chemical conversion treatment agent having a pH of 1.5 to 4.0 is used.

  Furthermore, in Patent Document 1, according to such a method, without using a treatment agent containing harmful chromium, it is excellent in performance such as corrosion resistance and adhesion of a coating film, and retains the glitter of aluminum. It is described that a coating film can be formed.

  Further, in Patent Document 2, after shot blasting is performed on a cast aluminum wheel, the aluminum wheel is subjected to (1) degreasing + non-chromate treatment, (2) degreasing + pickling + non-chromate treatment, or (3 ) A pretreatment method for performing degreasing + pickling + non-chromate treatment + organic treatment is described.

  In Patent Document 3, an aluminum wheel is cast, subjected to heat treatment, shot blasted, and then treated with a strong alkaline aqueous solution or alkaline electrolyzed water, so that shot grains (iron) remaining on the aluminum wheel surface can be obtained. A method is disclosed in which surrounding aluminum is melted to expose and remove iron from the aluminum wheel surface.

  By the way, although it is not related to the manufacturing method of an aluminum wheel, the technique disclosed by patent document 4 is known as a technique which improves the corrosion resistance of an aluminum base material, and adhesiveness with a coating film, for example.

  Specifically, Patent Document 4 describes that an acid heat cleaner is used to pickle an aluminum heat exchanger, followed by chemical conversion treatment film formation and hydrophilic film formation.

  It is described that an aqueous solution containing at least one metal selected from iron, nickel, cobalt, molybdenum, and cerium and / or a salt of a metal acid and nitric acid and / or sulfuric acid is used as the acidic detergent. Yes. Moreover, it is described that the density | concentration of the metal salt and / or metal acid salt in the said aqueous solution is 0.01-5 mass%.

Patent Document 4 describes that, according to such a configuration, the aluminum heat exchanger is less likely to generate white rust, and also has high adhesion to the hydrophilic coating film.
JP 2000-282251 A (published October 10, 2000) JP 2002-88492 A (published March 27, 2002) Japanese Patent Laying-Open No. 2007-107069 (published on April 26, 2007) JP 2001-158983 A (published June 12, 2001)

  By coating the aluminum wheel treated by the techniques disclosed in Patent Documents 1 to 3, the adhesion of the coating film to the aluminum wheel and the corrosion resistance of the painted aluminum wheel can be improved to some extent. However, as a practical painted aluminum wheel, it cannot be said that both coating film adhesion and corrosion resistance are sufficient.

  Moreover, although the technique of patent document 4 is a surface treatment method of an aluminum-type base material, since the use of the aluminum-type base material of patent document 4 is a completely different heat exchanger from an aluminum wheel, The physical properties required for the substrate are completely different. Therefore, the characteristics of the aluminum-based substrate are also completely different. Therefore, it is impossible to improve the corrosion resistance and the adhesion with the coating film, which are problems in the aluminum wheel, using the technique of Patent Document 4.

  Moreover, the technique of patent document 4 aims at the removal of the segregated material and aluminum-silicon alloy which are caused by the brazing material on an aluminum material. Therefore, the technique of Patent Document 4 cannot remove metal impurities that are nobler than aluminum metal, which is a cause of deterioration in adhesion and corrosion resistance of aluminum wheels.

  In the first place, in the prior art as disclosed in the above-mentioned Patent Documents 1 to 3, the reason why the adhesion to the coating film and the corrosion resistance cannot be sufficiently improved in the painted aluminum wheel is unknown. there were. For this reason, it has not been possible to take measures to develop a technique for improving the adhesion and corrosion resistance of the painted aluminum wheel to the effective range of the practical level.

  This invention is made | formed in view of the said problem, Comprising: The objective is to provide the manufacturing method of an aluminum wheel which has high corrosion resistance and high adhesiveness with a coating film, and an aluminum wheel.

  As a result of intensive studies in view of the above problems, the present inventors have found that the surface of an aluminum-based substrate that has been pre-painted using conventional techniques such as Patent Documents 1 to 3, such as iron, nickel, copper, etc. We have found that there are more precious metal impurities than aluminum.

  Specifically, the present inventors use an X-ray photoelectron spectroscopy that can analyze the extreme surface layer, and the surface of the aluminum-based substrate after casting and / or forging is oxidized with poor properties as a coating base. In addition to the film, the inventors have uniquely found that noble metal impurities (iron, nickel, copper, etc.) (hereinafter also referred to as “metal impurities”) are segregated with respect to aluminum.

  In addition, on the surface of an aluminum-based substrate that has been pre-painted using conventional techniques such as treatment by physical means such as shot blasting, or chemical etching using an alkali treatment solution or an acid treatment solution on the surface of an aluminum wheel. And found that there is a lot of metal segregation.

  Furthermore, it has been uniquely found that this metal impurity can be removed by washing the surface of the aluminum-based substrate with an acidic solution having a specific composition. Further, it has been uniquely found that if an acidic solution having a specific composition is used, the aluminum oxide film can be removed as in the case of a conventional acidic solution.

  In addition, when a coating film is formed on the surface of an aluminum-based substrate washed with such an acidic solution, the adhesion between the coating film and the aluminum-based substrate is improved, and the coated aluminum-based substrate It was found uniquely that the corrosion resistance of the material can be improved.

  Furthermore, after performing a release agent removing step of removing the release agent by physical means and / or chemical means from the surface of an aluminum wheel formed by molding an aluminum base material, the above acidic solution is used. It has been found that by performing cleaning, an aluminum wheel having high corrosion resistance and high adhesion to a coating film can be produced even when casting or forging using a large amount of a release agent. In particular, when the amount of the release agent used is large, the release agent is removed in advance by physical means and / or chemical means, compared to the technique of performing only pickling using an acidic solution having a specific composition. It has been found that the effect of pickling can be increased by placing the aluminum wheel, and the high corrosion resistance of the aluminum wheel and the high adhesion to the coating film can be further improved.

  The present inventors have completed the present invention based on these uniquely found findings. That is, the present invention includes the following industrially useful inventions.

(1) A mold release agent removing step for removing the mold release agent from the surface of an aluminum wheel formed by molding an aluminum base material or an aluminum alloy base material by physical means and / or chemical means, and the above-mentioned release agent removal. After the step, the metal in the pickling step includes a pickling step of washing with an acidic solution containing a metal ion of 0.5 g / L to 10 g / L and nitric acid of 10 g / L to 100 g / L. Ion contains at least 1 sort (s) of metal ion selected from the group which consists of Fe3 ⁺ ion, Ni2 ⁺ ion, Co2 ⁺ ion, ^{Mo6 +} ion, and Ce4 ⁺ ion, The manufacturing method of the aluminum wheel characterized by the above-mentioned.

  (2) The method for producing an aluminum wheel according to (1), wherein the acidic solution further contains sulfuric acid of more than 0 g / L and not more than 50 g / L.

  (3) In the said acidic solution, the weight ratio of the sulfuric acid with respect to nitric acid is less than 1/3, The manufacturing method of the aluminum wheel as described in (2) characterized by the above-mentioned.

  (4) In the release agent removing step, the release agent is removed by at least one physical means selected from the group consisting of barrel polishing, brush polishing, buffing, and high-pressure water washing (1 The manufacturing method of the aluminum wheel of any one of (3)-(3).

  (5) The aluminum according to any one of (1) to (3), wherein in the release agent removing step, the physical means is treated by shot blasting and then chemical means. Wheel manufacturing method.

  (6) The method for producing an aluminum wheel according to any one of (1) to (5), wherein the chemical means is chemical etching using an alkali treatment liquid or an acid treatment liquid.

(7) The chemical etching method for aluminum wheel according to any one of wherein the etching 1000 mg / ^{m 2} or more 40000mg / ^{m 2} or less of the surface of the aluminum wheel (1) to (6).

  (8) On the surface of the aluminum wheel in the pickling step, the weight ratio of copper to aluminum (Cu / Al) is 0.1 or less, and the weight ratio of iron to aluminum (Fe / Al) is 0.00. 1 or less, and the weight ratio (Ni / Al) of nickel and aluminum is 0.1 or less, The manufacturing method of the aluminum wheel in any one of (1)-(7) characterized by the above-mentioned.

  (9) The method for producing an aluminum wheel according to any one of (1) to (8), wherein the pickling step further includes a chemical conversion treatment step of chemical conversion treatment of the surface of the aluminum wheel.

  (10) The method for manufacturing an aluminum wheel according to (9), further comprising a coating step of coating the surface of the aluminum wheel after the chemical conversion treatment step.

  (11) The method for manufacturing an aluminum wheel according to (10), wherein the coating is powder coating.

  (12) An aluminum wheel manufactured using the method for manufacturing an aluminum wheel according to (10) or (11).

As described above, the method for producing an aluminum hole according to the present invention removes a release agent from the surface of an aluminum wheel formed by molding an aluminum base material by physical means and / or chemical means. And a pickling step of washing with an acidic solution containing 0.5 g / L or more and 10 g / L or less of metal ions and 10 g / L or more and 100 g / L or less of nitric acid after the release agent removing step. And the metal ions in the pickling step include at least one metal ion selected from the group consisting of Fe ³⁺ ions, Ni ²⁺ ions, Co ²⁺ ions, Mo ⁶⁺ ions, and Ce ⁴⁺ ions. It is said.

  Therefore, in particular, even when casting or forging using a large amount of mold release agent, the mold release agent present on the surface of the aluminum wheel, metal impurities nobler than aluminum, and the original aluminum oxide The film can be removed efficiently.

  Therefore, when coating is performed on an aluminum wheel whose surface has been washed with the acidic solution, it is possible to improve coating adhesion and coating corrosion resistance.

  An embodiment of the present invention will be described as follows, but the present invention is not limited to this. In the present specification, “A to B” indicating a range means A or more and B or less.

  The method for producing an aluminum wheel according to the present invention includes a release agent removing step of removing the release agent from the surface of the aluminum wheel formed by molding an aluminum base material by physical means and / or chemical means.

  In the method for producing an aluminum wheel according to the present invention, after the release agent removing step of removing the release agent by the above physical means and / or chemical means, the surface of the aluminum wheel is 0.5 g / L to 10 g / At least a step of washing with an acidic solution containing L metal ions and 10 g / L to 100 g / L of nitric acid (hereinafter also referred to as “pickling step”) is included.

  By including the above pickling process, the pickling process removes impurities and smuts existing on the surface of the aluminum wheel that is not removed in the release agent removing process, and the metal element noble than aluminum. The surface of the can be cleaned.

  Therefore, when the surface of the aluminum wheel is coated, the adhesion of the coating film formed by the coating to the aluminum wheel can be improved.

  In addition, the process by "physical means" in this specification means performing the process accompanied by a physical contact with respect to an aluminum wheel, and changing the surface property of an aluminum wheel. Further, the treatment by “chemical means” means that the surface properties of the aluminum wheel are changed by performing a process involving contact with a chemical on the aluminum wheel.

  By the release agent removing step, the release agent that is difficult to remove in the pickling step can be efficiently removed. For this reason, in particular, even when casting or forging using a large amount of a release agent, it is possible to realize a method for producing an aluminum wheel having high corrosion resistance and high adhesion to a coating film.

  In addition, the method for producing an aluminum wheel according to the present invention is a step of removing oil adhering to the surface of the aluminum wheel (hereinafter also referred to as a “degreasing step”) after the physical means and / or before the chemical means. ) May be included.

  The method for producing an aluminum wheel according to the present invention may include a step of forming a chemical conversion film for improving adhesion and corrosion resistance of the coating film (hereinafter, also referred to as “chemical conversion step”) after the pickling step. preferable.

  By performing the chemical conversion step, when the surface of the aluminum wheel is coated, the adhesion of the coating film formed by the coating to the aluminum wheel can be further improved.

  Moreover, the manufacturing method of the aluminum wheel concerning this invention is the process for improving the adhesiveness with the aluminum wheel of this coating film after the said pickling process (in the structure containing a chemical conversion process, after a chemical conversion process). (Hereinafter, also referred to as “post-processing step”).

  By performing the post-processing step, it is possible to widen the selection range of the type of coating applied to the aluminum wheel. If it demonstrates more concretely, even if it is a case where the coating which forms a thick film with high internal stress is given like powder coating, the adhesiveness with the aluminum wheel of a coating film can be improved.

  Furthermore, the manufacturing method of the aluminum wheel concerning this invention may include the coating process after the said chemical conversion process (after a post-processing process in the structure containing a post-processing process). Thereby, the painted aluminum wheel can be manufactured.

  In the present invention, the aluminum wheel may be an aluminum wheel formed by molding, in other words, casting an aluminum-based substrate. In particular, an aluminum wheel formed by molding AC4C or AC4CH specified by JIS H5202 is preferable. Aluminum alloy base materials such as AC4C and AC4CH can be suitably used for aluminum wheels. The aluminum wheel in the present invention may be an aluminum wheel formed by forging an aluminum base material. In particular, an aluminum wheel formed by molding 6061 defined by JIS H 4000 is preferable.

  Although the said aluminum-type base material may consist only of aluminum or an aluminum alloy, the other metal may be included intentionally or as an impurity.

  As said other metal, the metal impurity normally contained in the aluminum-type base material used as a raw material of an aluminum wheel, the metal added intentionally, etc. can be mentioned. Specifically, for example, strontium may be added to improve mechanical properties.

  Here, each step that can be included in the method for producing an aluminum wheel according to the present invention, that is, a step by a physical means (release agent removing step), a step by a chemical means (release agent removing step), a degreasing step, The pickling process, the chemical conversion treatment process, the post-treatment process, and the coating process will be described more specifically.

  As described above, the method for producing an aluminum wheel according to the present invention only needs to include at least the release agent removing step and the pickling step among the above steps, and needs to include all steps. There is no.

  Specifically, the method for producing an aluminum wheel according to the present invention includes: (i) a mold release agent that is processed by at least one physical means selected from the group consisting of barrel polishing, brush polishing, buff polishing, and high-pressure water washing. A method including a removal step and a pickling step, or (ii) a method including a release agent removing step of treating by chemical means after processing by shot blasting, and a pickling step is preferred, (i) or A method including the step (ii) and the chemical conversion treatment step is more preferable, and a method including the step (i) or (ii), the chemical conversion treatment step, and the coating step is particularly preferable.

(I) Process by physical means (release agent removing process)
A mold release agent or an aluminum oxide film remains on the surface of the aluminum wheel after casting and / or forging. For this reason, it is preferable to perform the process which removes the said mold release agent and an aluminum oxide film by a physical means.

  Specific examples of the physical means include shot blasting, barrel polishing, brush polishing, buffing, and high-pressure water washing. In addition, barrel polishing, brush polishing, and buff polishing are processing methods conventionally used for processing aluminum wheels, and are inferior to shot blasting in terms of productivity. Was not generally used.

  Examples of the barrel polishing include a method using the apparatus shown in FIG. Specifically, as shown in FIG. 2, the tank 2 is filled with an abrasive such as alumina and water, and is pushed in the A direction and the B direction while rotating the aluminum wheel 1 (forward and reverse). This is a method for polishing the surface of the aluminum wheel 1. In the tank 2, a compound or the like may be mixed with water as a lubricating auxiliary material.

  Examples of the brush polishing include a method using the apparatus shown in FIGS. Specifically, in the case where the apparatus shown in FIG. 3 is used, as shown in FIG. 3, the brush 3 that is rotated (forward and reverse) while rotating (forward and reverse) the aluminum wheel 1 is moved to A ′. This is a method of polishing while pressing in the direction and sliding in the B ′ direction.

  In the case of using the apparatus shown in FIG. 4, as shown in FIG. 4, the aluminum wheel 1 or the brush 3 is pressed in the A ″ direction while being rotated (forward or reverse) and polished.

  Examples of the buffing include a method in which the same apparatus as that shown in FIGS. 3 and 4 is used, and polishing is performed using a cloth or the like coated with an abrasive instead of the brush 3.

  The high-pressure water washing can be performed by washing the wheel surface with a water pressure of 200 MPa, for example.

  On the other hand, when the mold release agent and the original aluminum oxide film are removed by shot blasting to an aluminum wheel as before, shot grains of iron-based metal such as iron or stainless steel used for shot blasting remain on the surface of the aluminum wheel. There are things to do. When iron as the shot grains remains on the surface of the aluminum wheel, it becomes a factor that hinders the adhesion between the surface of the aluminum wheel and the coating film. Further, moisture in the atmosphere may permeate the coating film and react with shot iron and aluminum of aluminum wheels, which may cause a decrease in corrosion resistance.

  For this reason, in the release agent removing step in the method for producing an aluminum wheel according to the present invention, a step (hereinafter, referred to as a step by at least one physical means selected from the group consisting of barrel polishing, brush polishing, buff polishing, and high-pressure water washing). It is preferable to carry out the treatment by a “physical process such as barrel polishing”.

  Due to the treatment by such physical means, the mold release agent and the poorly oxidized aluminum oxide film adhered to the surface during the molding of the aluminum wheel, organic impurities such as machine oil and cutting oil adhering to the surface of the aluminum wheel, etc. Can be removed.

  Furthermore, since the manufacturing method of the aluminum wheel concerning this invention is the structure containing the pickling process mentioned later, an impurity can be removed more efficiently.

(II) Process by chemical means (release agent removal process)
Specific examples of the chemical means include chemical etching using an alkali treatment liquid or an acid treatment liquid.

  In the method for producing an aluminum wheel according to the present invention, a step by chemical means for chemically etching the surface of the aluminum wheel using an alkali treatment solution or an acid treatment solution before the pickling step (hereinafter referred to as “chemical etching step”). (Also referred to as).

  By performing the chemical etching step, the release agent and the original aluminum oxide film present on the surface of the aluminum wheel can be efficiently removed. That is, the surface of the aluminum wheel can be cleaned to a higher degree by combining with the later-described pickling step.

  In the above chemical etching process, when shot blasting is performed on the mold release agent and the original aluminum oxide film adhered during casting and / or forging (molding) of the aluminum wheel, and the aluminum wheel cast and / or forged (molded). Can efficiently remove shot grains and iron originating from the shot grains.

  In the chemical etching process, the surface of the aluminum wheel is chemically etched. The aluminum wheel subjected to this chemical etching step may be as it is removed from the mold after being cast and / or forged, or shot blasted against the surface after being removed from the mold. It may be one that has been subjected to a physical process such as barrel polishing, or may be one obtained by degreasing the surface of the aluminum wheel in the above degreasing process.

  Especially, in this invention, it is preferable that the aluminum wheel provided to the said chemical etching process is an aluminum wheel which carried out physical processes, such as shot blasting or barrel grinding | polishing, after removing from the type | mold.

  Furthermore, according to the said chemical etching process, the aluminum oxide film with a bad property produced | generated on the surface of an aluminum wheel at the time of casting and / or forging of an aluminum-type base material can be removed.

  In addition, when the aluminum wheel subjected to the chemical etching step is, for example, an aluminum wheel that has been subjected to shot blasting, the surface of the aluminum wheel is etched, and the shot grains remaining on the surface of the aluminum wheel ( The shot grains (iron) can be removed by dissolving aluminum around the iron.

  The chemical etching solution used in the chemical etching step is not particularly limited, and any conventionally known chemical etching solution can be used. Specifically, the chemical etching treatment liquid can be classified into an acid type and an alkali type.

  Examples of the acid-based chemical etching treatment liquid include an acidic solution containing at least one acid selected from mineral acids such as sulfuric acid, hydrofluoric acid, nitric acid, and phosphoric acid. Further, such an acid-based chemical etching treatment solution may contain an oxidizing agent such as nitrite ion, hydrogen peroxide, and ferric ion in order to improve the etching property of the aluminum wheel.

  Examples of the alkaline chemical etching treatment liquid include an alkaline solution selected from sodium hydroxide, potassium hydroxide, and alkali metal phosphate. The pH of these alkaline chemical etching treatment solutions is not particularly limited, but is preferably 12.0 or more, and more preferably 12.5 or more.

  Moreover, as an alkaline chemical etching treatment solution, alkaline electrolyzed water having a pH of 10.5 to 11.7 can also be used. Examples of the alkaline electrolyzed water include a catholyte produced by electrolyzing a potassium carbonate aqueous solution in an electrolytic cell and generated on the cathode side of the electrolytic cell.

  In order to make chemical etching more uniform, a surfactant may be added to such an alkaline chemical etching treatment solution.

  Moreover, in order to prevent that aluminum elutes from an aluminum wheel and the washing | cleaning efficiency falls, you may contain the chelating agent which capture | acquires aluminum ion. Examples of the chelating agent include citric acid, succinic acid, tartaric acid, gluconic acid, and salts thereof.

  The processing temperature in the chemical etching step is not particularly limited, and may be a temperature range that is normally performed. Specifically, it is generally preferable to carry out at 20 ° C. to 70 ° C., and more preferably at 35 ° C. to 60 ° C. Moreover, you may perform a chemical etching process in the heated state for the purpose of improving workability | operativity. However, even in that case, the treatment temperature is preferably lower than 80 ° C. When the chemical etching step is performed at 80 ° C. or higher, the water tends to evaporate quickly and the processing temperature tends to change.

  In addition, in the chemical etching step, when the chemical etching is performed by immersing the aluminum wheel in the chemical etching treatment solution, it is preferable to perform ultrasonic treatment in the chemical etching treatment solution. According to such a configuration, the chemical etching reaction can be promoted. The chemical etching reaction promoted by the ultrasonic treatment is due to the effects of micro vibration, stirring, defoaming, cavitation, and the like.

In Chemical etching step, is not particularly limited amount of etching aluminum wheels, specifically, it is preferable that the etching amount of ^{1000mg / m 2 ~40000mg / m 2} , 1000mg / m 2 ~ more preferably to 20000 mg / ^{m 2,} and even more preferably to a ^{1000mg / m 2 ~5000mg / m 2} .

The amount of etching is determined by weighing an aluminum alloy test piece (stretched material, 5000 series, length 150 mm × width 70 mm × thickness 0.8 mm; total area 210 cm ^{2 on} both sides) in advance with alkali degreasing, washing with water and drying. Keep it. The alkaline degreasing is performed using an alkaline degreasing agent (Surf Cleaner 53NF, manufactured by Nippon Paint Co., Ltd.).

Next, after carrying out a predetermined chemical etching process, the test piece after chemical etching is weighed by washing with water and drying. And the weight loss per processing area before and behind chemical etching (P) can be calculated | required, and it can convert and calculated in the elution amount per m < ² > using the following formula | equation.
Etching amount A (mg / m ² ) = P (mg) × 10000 ÷ 210
In the chemical etching step, it is preferable to perform a water washing treatment on the aluminum wheel after the chemical etching treatment. Accordingly, the chemical etching treatment liquid can be washed away (diluted) to stop the chemical etching reaction. Moreover, the amount of the chemical etching treatment liquid brought into a subsequent process can be reduced by the water washing treatment.

  The water washing treatment may be performed under conditions that can stop the chemical etching reaction, but is preferably performed a plurality of times from the viewpoint of efficiency. Thereby, a chemical etching reaction can be stopped reliably.

(III) Degreasing step The degreasing step is a step of removing oil adhering to the surface of the aluminum wheel.

  The aluminum wheel to be subjected to the degreasing process may be in a state of being removed from the mold after being cast and / or forged, or after being removed from the mold, the surface may be physically polished such as barrel polishing. It may be processed by a typical process or may be shot blasted.

  In the degreasing step, the method of degreasing the surface of the aluminum wheel is not particularly limited, and a conventionally known method used for degreasing the surface of the aluminum base material may be used.

  Specifically, the degreasing treatment can be generally performed by alkali degreasing, acid degreasing, or the like. Examples of the alkali used for alkali degreasing include caustic soda, sodium silicate, sodium carbonate, and sodium phosphate. In addition, a surfactant may be added to the alkali.

  Examples of the acid used for acid degreasing include sulfuric acid and nitric acid.

  In such alkali degreasing and acid degreasing, the degreasing treatment may be performed by immersing an aluminum wheel in a solution containing the alkali or acid, or spraying the solution on the aluminum wheel. Especially, in order to perform degreasing effectively, it is preferable to carry out by the immersion method.

(IV) Pickling step In the pickling step, the surface of the aluminum wheel is washed with an acidic solution having a specific composition.

  The aluminum wheel subjected to the pickling process may be an aluminum wheel subjected to a physical process such as barrel polishing on the surface after being removed from the mold, and further, the aluminum wheel was subjected to a degreasing process. It may be a thing. Further, it may be removed from the mold and subjected to the degreasing step after shot blasting, and further subjected to the chemical etching step, or may be subjected to a degreasing step after being removed from the mold and then subjected to a physical process such as brush polishing. Moreover, after removing from a type | mold, you may use for the said chemical etching process, without using for the said degreasing process.

  Among them, in the present invention, the aluminum wheel to be subjected to the pickling step is (i) an aluminum wheel treated by at least one physical means selected from the group consisting of barrel polishing, brush polishing, buff polishing, and high-pressure water washing, Or (ii) an aluminum wheel that has been removed from the mold, or an aluminum wheel that has been shot blasted on the surface after being removed from the mold and further processed by chemical means.

  In the aluminum wheel of (i), since it processed by the said specific physical means, impurities, such as iron, and a mold release agent do not remain on the surface of an aluminum wheel. The aluminum wheel of (ii) is processed by shot blasting, but since chemical processing such as a chemical etching process is performed after that, impurities such as iron and a release agent are present on the surface of the aluminum wheel. It does not remain.

  According to the release agent removing step, as described above, the release agent, shot residue, oil, and dirt attached to the surface of the aluminum wheel are effectively removed. The surface of the aluminum wheel from which the release agent, shot residue, oil, and dirt have been removed in such a release agent removal step is more than an aluminum oxide film formed during casting and / or forging, or aluminum such as Cu. Noble metal elements (metal impurities) are exposed.

  The aluminum oxide film and metal impurities generated during casting and / or forging exposed on the surface of the aluminum wheel, when the aluminum wheel is coated, the adhesion between the coating film and the aluminum wheel and the painted aluminum wheel. It will cause a decrease in the corrosion resistance.

  More specifically, an aluminum hole formed by a conventionally known casting and / or forging method generally has a mold release agent before the mold release agent removing step, as shown in FIG. A fragile surface oxide film layer (hereinafter also referred to as “release agent-impregnated layer”) that has been sintered and / or impregnated is formed on the surface. A metal impurity uneven distribution layer is formed under the release agent-impregnated layer. An aluminum cast or forged alloy layer (aluminum cast alloy layer) exists below the metal impurity uneven distribution layer.

  By subjecting the aluminum wheel in this state to the release agent removing step, the release agent-impregnated layer is removed as shown in FIG. A new surface oxide film layer in which metal impurities are unevenly distributed is formed on the surface of the aluminum wheel from which the release agent-impregnated layer has been removed. That is, in this new surface oxide film layer, the release agent is not contained and the metal impurities are concentrated.

  Thus, the surface where the metal impurities are unevenly distributed promotes the corrosion reaction on the surface of the aluminum wheel.

  However, according to the pickling process according to the present invention, it is possible to remove a metal element nobler than aluminum such as Cu existing on the surface of the aluminum wheel in the release agent removing process. In other words, according to the pickling process, an oxide film layer free from uneven distribution of metal impurities can be formed on the surface of the aluminum wheel, as shown in FIG. Such an oxide film layer does not contain metal impurities.

  Therefore, when the aluminum wheel is coated, the adhesion between the coating film and the aluminum wheel and the corrosion resistance of the painted aluminum wheel can be improved.

  The metal element (metal impurity) nobler than the aluminum is not limited to Cu, and examples thereof include Fe and Ni.

  Moreover, according to the said pickling process, the smut, stain | pollution | contamination, and oxide film which exist on the surface of the aluminum wheel remaining at the mold release agent removal process can be removed. These smuts, dirt, and oxide films also reduce the adhesion of the coating film formed on the aluminum wheel by painting to the aluminum wheel. Therefore, according to the said pickling process, the adhesiveness to the aluminum wheel of the coating film formed on an aluminum wheel in the coating process mentioned later can be improved.

The smut removed in the pickling step is not particularly limited, and specific examples include a mixture of insoluble components such as carbon, magnesium oxide, and Fe ₃ O ₄ .

  In the pickling process, first, the aluminum wheel is treated with an acidic solution containing metal ions, nitric acid, and sulfuric acid. In addition, in the said acidic solution, a sulfuric acid is not an essential component and can also be set as the structure which does not contain a sulfuric acid.

  The concentration of metal ions in the acidic solution is preferably 0.5 g / L to 10 g / L, and more preferably 1 g / L to 5 g / L.

  When the concentration of the metal ions is less than 0.5 g / L, the metal impurity removal effect tends to be reduced. On the other hand, if it exceeds 10 g / L, the cost tends to increase. However, within the above range, metal impurities can be efficiently removed while suppressing the manufacturing cost.

In the present invention, the acidic solution contains at least one metal ion selected from the group consisting of Fe ³⁺ ions, Ni ²⁺ ions, Co ²⁺ ions, Mo ⁶⁺ ions, and Ce ⁴⁺ ions as the metal ions. It only has to be. In particular, it preferably contains Fe ³⁺ ions and / or Ce ⁴⁺ ions.

By using Fe ³⁺ ions, metal impurities can be removed more efficiently.

  The source of the metal ions is not particularly limited, and specific examples include metal salts and / or metal acid salts selected from the group consisting of iron, nickel, cobalt, molybdenum and cerium. it can.

More specifically, as a source of the Fe ³⁺ ions, for example, a water-soluble ferric salt such as Fe ₂ (SO ₄ ) ₃ , Fe (NO ₃ ) ₃ , Fe (ClO ₄ ) ₃ ; FeSO ₄ And water-soluble ferrous salts such as Fe (NO ₃ ) ₂ .

When the water-soluble ferrous salt is used as a source of the Fe ³⁺ ions, an equivalent amount of oxidizing agent is added to the acidic aqueous solution containing the water-soluble ferrous salt, and a necessary amount of Fe ²⁺ ions is added. Is preferably used after being oxidized to Fe ³⁺ ions.

Examples of the Ni ²⁺ ion supply source include nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate.

Examples of the source of Co ²⁺ ions include cobalt sulfate, cobalt ammonium sulfate, cobalt nitrate, cobalt acetate, and cobalt chloride.

Examples of the source of Mo ⁶⁺ ions include molybdenum chloride, ammonium molybdate, potassium molybdate, sodium molybdate, and the like.

  Examples of the cerium ion supply source include cerium sulfate, cerium ammonium sulfate, cerium acetate, cerium nitrate, and cerium chloride.

  The concentration of nitric acid in the acidic solution is preferably 10 g / L to 100 g / L, and more preferably 50 g / L to 100 g / L. If the concentration of nitric acid is 10 g / L or less, the metal impurity removal effect tends to be reduced. On the other hand, when the concentration of nitric acid exceeds 100 g / L, the cost tends to increase. However, within the above range, metal impurities can be efficiently removed while suppressing the manufacturing cost.

  The concentration of sulfuric acid in the acidic solution is preferably 0 g / L to 50 g / L, and more preferably 0 g / L to 10 g / L.

  Further, in the acidic solution, the weight ratio of sulfuric acid to nitric acid is preferably 1 or less, and more preferably less than 1/3.

The pH of the acidic solution is not particularly limited, but if the pH is too low, the surface of the aluminum wheel may be excessively etched. On the other hand, if the pH is too high, the etching rate of the aluminum wheel is extremely reduced, and the surface of the aluminum wheel tends to be unable to be efficiently cleaned. Therefore, generally, the pH of the acidic solution is preferably 0 to 2, and more preferably 0.05 to 1. The pH of the acidic solution is preferably adjusted with HNO ₃ which is a nitrate ion supply source.

  If necessary, hydrochloric acid, phosphoric acid, hydrofluoric acid, or a compound of these acids may be added to the acidic solution alone or in admixture of two or more. Furthermore, you may add a fluorine ion, surfactant, etc.

  Moreover, in order to improve the pickling effect, you may mix | blend an oxidizing agent with the said acidic solution. Specific examples of the oxidizing agent include a low oxidation number Mo compound, hydrogen peroxide, and nitrite.

  In addition, the acidic solution (in other words, washing | cleaning liquid) used in the pickling process demonstrated above is also contained in this invention.

  In the pickling step, the method of treating the aluminum wheel with the acidic solution is not particularly limited. Specifically, for example, the method of spraying the acidic solution on the surface of the aluminum wheel or the acidic solution is used. The method etc. which immerse an aluminum wheel in the pickling bath which put in can be mentioned.

  The treatment temperature and treatment time when the aluminum wheel is treated with the acidic solution are not particularly limited. Specifically, the treatment temperature is preferably 10 ° C to 70 ° C, and more preferably 40 ° C to 60 ° C.

  By processing within the processing temperature range, the surface of the aluminum wheel can be more efficiently cleaned.

  In addition, the treatment time, in other words, the contact time between the aluminum wheel and the acidic solution is preferably 30 seconds to 5 minutes, and more preferably 60 seconds to 3 minutes. By treating within the treatment time, the surface of the aluminum wheel can be efficiently cleaned.

  In the pickling step, the aluminum wheel is preferably washed with water after being treated with the acidic solution. Thereby, an acidic solution can be washed away (diluted) and pickling can be stopped. Moreover, the amount of the acidic solution brought into a subsequent process can also be reduced by this water washing treatment.

  This water washing treatment may be performed under conditions that allow the pickling to be stopped, but is preferably performed a plurality of times from the viewpoint of efficiency. Thereby, pickling can be stopped reliably.

  On the surface of the aluminum wheel after the pickling step, the weight ratio of copper to aluminum (Cu / Al) is 0.1 or less, and the weight ratio of iron to aluminum (Fe / Al) is 0.1 or less. And the weight ratio of nickel to aluminum (Ni / Al) is preferably 0.1 or less.

  According to the said structure, when coating the aluminum wheel after the said pickling process (or after the chemical conversion treatment process and / or post-processing process mentioned later), improving adhesiveness with a coating film, and corrosion resistance Can do.

Cu / Al, Fe / Al, and Ni / Al on the surface of the aluminum wheel can be measured by surface analysis by X-ray photoelectron spectroscopy (XPS method). The analysis depth is about 10 mm (1 nm, 10 ⁻³ μm) from the surface.

(V) Chemical conversion treatment step In the chemical conversion treatment step, a chemical conversion film is formed on the surface of the aluminum wheel treated in the pickling process to improve adhesion to the coating film and corrosion resistance. Specifically, a uniform and dense chemical conversion film is formed in close contact with the base of the aluminum wheel.

  The specific chemical conversion treatment in the chemical conversion treatment step is not particularly limited, and a conventionally known chemical conversion treatment applied to the surface of the aluminum wheel may be performed.

  The chemical conversion treatment agent used for the chemical conversion treatment is not particularly limited, and a conventionally known chemical conversion agent may be appropriately selected and used according to the type of chemical conversion treatment. Specifically, for example, chromate conversion agent such as chromate chromate, phosphate chromate, zirconium salt, titanium salt, silicon salt, boron salt or permanganate and fluoride thereof, or phosphoric acid with these, It can be used as a chromium-free chemical conversion treatment agent comprising manganic acid, permanganic acid, vanadic acid, tungstic acid, and molybdic acid.

  As the chromium-free chemical conversion treatment agent, more specifically, zirconium ions or titanium ions 0.01 g / L to 0.125 g / L, phosphate ions 0.01 g / L to 1.0 g / L, and fluorine An acidic film chemical conversion treatment agent containing 0.01 g / L to 0.5 g / L of ions and having a pH of 1.5 to 4.0, preferably pH 2.8 to 3.8 can be mentioned.

  According to such an acidic film chemical conversion treatment agent, it is possible to form a chemical conversion film sufficient to exhibit performance such as corrosion resistance, and the chemical conversion film becomes too thick, and the brightness of the aluminum wheel is impaired. Can be prevented.

In the acidic film chemical conversion treatment agent, examples of the supply source of zirconium ions include soluble fluorozirconates such as fluorozirconate and fluorozirconate; (NH ₄ ) ₂ ZrF ₆ ; alkali metal fluorozirconate; zirconium fluoride Etc. can be used.

Moreover, as a supply source of titanium ions, for example, soluble fluorotitanate such as fluorotitanate or fluorotitanate; (NH ₄ ) ₂ TiF ₆ ; alkali metal fluorotitanate; titanium fluoride or the like can be used.

  Furthermore, as a phosphate ion supply source, for example, a phosphoric acid compound soluble in an acid solution such as phosphoric acid, ammonium phosphate, or alkali metal phosphate can be used. In particular, orthophosphoric acid is preferably used as a phosphate ion supply source, but is not limited thereto, and metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, hypophosphoric acid, and salts thereof may be used.

  In the acidic film chemical conversion treatment agent, phosphate ions are one of the film forming components, and contribute to the corrosion resistance and coating film adhesion of the formed chemical conversion film.

  Moreover, in the said acidic film chemical conversion treatment agent, as a supply source of a fluorine ion, it is soluble in the said acidic film chemical conversion treatment agent, can form a complex with aluminum, and has a reaction with respect to the said chemical conversion treatment. What does not exhibit an effect may be used. Specifically, for example, hydrofluoric acid, hydrofluoric acid salt, fluoboric acid, and the like can be given.

  When the above-mentioned zirconium or titanium complex is used as the fluorine ion supply source, it is preferable to use the fluorine compound in combination because the amount of fluorine ions produced is insufficient.

  In the acidic film chemical conversion treatment agent, fluorine ions serve as an aluminum etching agent. Therefore, when the fluorine ion concentration in the acidic film chemical conversion treatment agent is below the above range, etching of the surface of the aluminum wheel tends to be insufficient, and the weight of the formed chemical film tends to be insufficient. On the other hand, if the fluorine ion concentration exceeds the above range, the surface of the aluminum wheel tends to be excessively etched, and the surface of the aluminum wheel tends to be in a glazed state covered with frost.

  The pH of the acidic film chemical conversion treatment agent may be adjusted using an acid or base that does not adversely affect the chemical conversion treatment. Specifically, for example, nitric acid, ammonium hydroxide; perchloric acid, sulfuric acid Etc. may be used. In addition, when using a sulfuric acid among the said acids, it is preferable that the pH of the said acidic film chemical conversion treating agent shall be 2 or more.

In the chemical conversion treatment step, such a chemical conversion treatment agent is used to form a chemical conversion film for improving the adhesion and corrosion resistance of the coating film. The weight of the chemical conversion film formed in the chemical conversion treatment step is 5 mg / m ^2. ˜50 mg / m ² is preferred. When the weight of the chemical conversion film is less than 5 mg / m ² , performance such as corrosion resistance may not be sufficiently exhibited. On the other hand, when the weight of the chemical conversion film exceeds 50 mg / m ² , not only may the film become too thick and the brightness of the aluminum wheel may be impaired, but the corrosion resistance may be inferior.

  The conditions for the chemical conversion treatment (treatment temperature and treatment time) are not particularly limited, and may be set so that the weight of the chemical conversion film to be formed is within the above range. In general, the treatment temperature is preferably 30 ° C to 50 ° C. The treatment time is preferably 30 seconds to 3 minutes. More specifically, preferable chemical conversion treatment conditions include a chemical conversion treatment condition at 40 ° C. for about 45 seconds.

  The specific method of the chemical conversion treatment is not particularly limited, and specific examples include an immersion method and a spray method.

  In the chemical conversion treatment step, it is preferable that the aluminum wheel is treated with the chemical conversion treatment agent and then washed with water. Thereby, the chemical conversion treatment agent can be washed away (diluted) to stop the chemical conversion treatment. Moreover, the amount of the chemical conversion treatment agent brought into a subsequent process can also be reduced by this water washing treatment.

  This water washing treatment may be performed under conditions that allow the chemical conversion treatment to be stopped, but is preferably performed a plurality of times from the viewpoint of efficiency. Thereby, a chemical conversion process can be stopped reliably.

(VI) Post-treatment step In the post-treatment step, the surface of the chemical conversion film formed on the surface of the aluminum wheel in the chemical conversion treatment step using a silane coupling agent or the like for the aluminum wheel treated in the chemical conversion treatment step. Then, a thin film is formed. The thin film formed in this post-treatment process improves the adhesion between the coating film and the aluminum wheel even when a thick coating film with high internal stress such as powder coating is formed on the surface of the aluminum wheel. Can be made.

  That is, if it is set as the structure containing the said post-processing process, the selection range of the kind of coating applied to an aluminum wheel can be expanded, and even if it is any coating, the adhesiveness of a coating film and an aluminum wheel can be improved.

  Although the processing agent used for a post-processing process is not specifically limited, A silane coupling agent can be used suitably. More specifically, for example, an aqueous solution containing an organoalkoxysilane compound can be used as the treatment agent.

  The said organoalkoxysilane compound has the effect | action which improves the adhesiveness of a coating film and an aluminum wheel in the said aqueous solution. The content of the organoalkoxysilane compound in the aqueous solution is preferably 0.1 g / L to 50 g / L, and more preferably 0.1 g / L to 10 g / L.

  When the content of the organoalkoxysilane compound is less than 0.1 g / L, the adhesion of the coating film may not be sufficiently improved. On the other hand, when the content of the organoalkoxysilane compound exceeds 50 g / L, the coating film may be unevenly attached and may be peeled off in a scab shape.

  The organoalkoxysilane compound is not particularly limited, but an organoalkoxy having at least one reactive functional group selected from the group consisting of a carbon-carbon double bond, an epoxy group, a mercapto group, and an amino group. A silane compound can be preferably used.

  More specifically, examples of such organoalkoxysilane compounds include γ-aminopropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidoxy. Examples thereof include propyltrimethoxysilane and γ-glycidoxypropyltriethoxysilane.

  Moreover, it is preferable that pH of the said aqueous solution is 10-12. If it is such a pH range, the said water-soluble stability is good and can post-process efficiently.

  In the post-processing step, the processing conditions (processing temperature, processing time, etc.) for performing the post-processing are not particularly limited, and may generally be set so as to obtain the effects of the post-processing steps described above. The treatment temperature is preferably 15 ° C. to 40 ° C. The treatment time is preferably 30 seconds to 60 seconds.

  In the post-treatment step, it is preferable to dry the aluminum wheel after treating the aluminum wheel with the aqueous solution. Thereby, the aluminum wheel can be efficiently painted in the painting process described later.

(VII) Coating process In a coating process, it coats on the surface of the aluminum wheel processed in the said chemical conversion treatment process, or the aluminum wheel processed in the said post-processing process. The coating is not particularly limited, and any conventionally known coating can be used. Specific examples include solvent coating, aqueous coating, and powder coating.

  Among them, it is preferable to use powder coating from the viewpoint of safety to the environment. In the conventional aluminum wheel manufacturing method, when powder coating is performed, the adhesion between the coating film and the aluminum wheel tends to be low. On the other hand, according to the method for producing an aluminum wheel according to the present invention, since the above pickling process is performed as a pretreatment for coating, even if powder coating is performed, there is an adverse effect on the adhesion with the coating film. In addition, a coated aluminum wheel having high adhesion with the coating film can be produced.

  The coating material used for the coating is not particularly limited, and may be appropriately selected according to the type of coating. In the case of solvent coating, it is preferable to use a high solid solvent paint with a small amount of organic solvent or an aqueous paint from the viewpoint of the environment.

  In the case of powder coating, acrylic resin, epoxy polyester resin, polyester resin, epoxy resin, or the like can be used.

  In the painting process, painting may be performed so that a plurality of coating layers are formed. Specifically, for example, powder primer coating, silver coating, and top clear coating may be applied in this order. For the powder primer coating, for example, a paint such as an acrylic resin, an epoxy polyester resin, a polyester resin, or an epoxy resin can be used. For top clear coating, it is preferable to use a paint such as an acrylic resin or a fluororesin in consideration of weather resistance.

  The present invention is not limited to the configurations described above, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of the present invention.

  Although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In addition, the shot residue and metal impurities on the aluminum wheel surface after the pickling process in the following examples and comparative examples were evaluated as follows. Moreover, the coating quality of the coated aluminum wheel was evaluated by the following impact test, SST test, CASS test, and yarn rust resistance test.

[Measurement of shot residue on aluminum wheel surface after pickling process]
A 30 mm x 30 mm x (thickness 2 to 30) mm sample with an analysis surface of a cast surface that has been shot blasted with SUS430 shot grains is a Rigaku scanning X-ray fluorescence analyzer ZSX Primus (manufactured by Rigaku Corporation). The residual amount of Fe, which is the main component of shot grains, was quantitatively analyzed by fluorescent X-ray analysis. The case where the Fe residual amount was 200 mg / m ² or less was rated as ◯, and the case where the Fe residual amount exceeded 200 mg / m ² was rated as x.

[Measurement of release agent residue on aluminum wheel surface after pickling process]
A sample of 5 mm × 5 mm × 5 mm (thickness) whose analysis surface is the surface of the workpiece (aluminum wheel) was analyzed by X-ray photoelectron spectroscopy under the following conditions after the pickling step.

  When a graphite-based mold release agent is used as the mold release agent, the C / Al ratio, which is a measure of the surface residue of the C component-containing mold release agent, is analyzed. The case was marked with x. When a kaolin / calcium salt release agent is used, the Ca / Al ratio, which is a measure of the residual amount of the surface of the release agent containing the Ca component, is analyzed. , 0.1 was exceeded.

[Measurement of metal impurities on aluminum wheel surface after pickling]
A sample of 5 mm × 5 mm × 5 mm (thickness) whose analysis surface is the surface of the workpiece (aluminum wheel) was analyzed by X-ray photoelectron spectroscopy under the following conditions after the pickling step. The relative weight ratio of each of Ni, Fe, and Cu, which becomes a factor for promoting corrosion of the aluminum alloy, was determined based on the following criteria.

  For each of the Ni / Al ratio, the Fe / Al ratio, and the Cu / Al ratio, 0.1 or less, each of the Ni / Al ratio, the Fe / Al ratio, and the Cu / Al ratio is 0.1. The case of exceeding X was marked with x.

[Impact test of painted aluminum wheel]
After cooling each obtained test piece to −30 ° C., it was attached to a sample holder of a stepping stone tester (manufactured by Suga Test Instruments Co., Ltd.) so that the stone entry angle would be 90 °, and 100 g of No. 7 crushed stone was attached. It sprayed with the air pressure of 3 kg / cm < ² >, and the crushed stone collided with the coating film of the test piece. The degree (number, size, location of destruction) of the scratches at that time was evaluated in three stages.

  As a result, ◯ indicates that no peeling of the coating film is observed, △ indicates that peeling of the coating film is partially observed, but no peeling damage reaching the substrate is detected, and peeling of the coating film reaching the substrate is scratched or scratched. What was recognized was made into x.

[SST test of painted aluminum wheel]
Salt spray test The surface of each test piece was cross-cut with a cutter knife, sprayed with salt water at 35 ° C. for 1200 hours using a 5 wt% NaCl aqueous solution, and the degree of corrosion within 2 mm around the cut portion was measured.

  As a result, the case where no blistering of the coating film was observed, the case where the blistering of the coating film within 2 mm occurred, and the case where the blistering of the coating film occurred exceeding 2 mm were marked as x.

[CASS test of painted aluminum wheel]
Cast test The surface of each test piece was cut to a length of 10 cm with a cutter knife, and the cast test solution prepared according to JISZ2371-2000 was sprayed at 50 ± 2 ° C. for 240 hours, and the degree of corrosion within 2 mm around the cut part Evaluated.

  As a result, those having no abnormalities such as blistering and rust of the coating film were blunt within 2 mm, or those in which rust was generated were Δ, those in which rust was generated exceeded 2 mm.

[Yarn rust resistance test of painted aluminum wheels]
Put a crosscut into the coating film, and carry out a cycle of “spraying with salt water for 24 hours, then wet (85% humidity, 40 ° C.) for 120 hours, and then air dry for 24 hours at room temperature”. The rust width on one side of the crosscut part was measured.

  As a result, those having no abnormalities such as blistering and rust of the coating film were blunt within 2 mm, or those in which rust was generated were Δ, those in which rust was generated exceeded 2 mm.

[Example 1: Production of painted aluminum wheel]
The molten aluminum alloy (AC4CH) was cast into an automotive wheel mold coated with a commercially available graphite release agent, cooled, and taken out from the mold.

  Next, heat treatment was performed. Next, as a physical treatment, shot blasting was performed using SUS430 material as shot grains. Further, as a physical treatment, barrel processing was carried out with the barrel polishing machine shown in FIG.

  Thereafter, degreasing (immersion treatment at 50 ° C. for 3 minutes) with an alkaline degreasing agent (Surf Cleaner 53NF (manufactured by Nippon Paint Co., Ltd.), 2% by weight) was performed. After the degreasing treatment, immersion water washing was performed in two steps.

Next, as a chemical treatment, an alkali etching treatment (treatment at 40 ° C. for 1 minute) with an alkali etching agent (Surf Cleaner SE300 (manufactured by Nippon Paint Co., Ltd.), 5% by weight) was performed. Then, immersion water washing was implemented in two steps. As a result of measuring the weight loss before and after the alkali etching treatment with a test piece for measuring the elution amount, the elution amount was 5 g / m ² .

  Then, it pickled with the acidic process liquid 2 of Table 1 (50 degreeC x 3 minute immersion). Immersion washing was carried out in two steps after the treatment.

After the pickling step, the amount of residual release agent, shot residue and metal impurities on the aluminum wheel surface were measured according to the above method using a chip obtained by cutting the cast surface of the casting wheel for surface analysis. As a result, as shown in Table 2, the Fe residual amount is 200 mg / m ² or less (◯), the release agent residue is also Ca / AL is 0.1 or less (◯), and the metal impurities are also Fe / Al is 0. Ni / Al was 0 and Cu / Al was 0.

  After the pickling process, it was subjected to chemical conversion treatment (pH = 3.5, 40 ° C., 45 seconds immersion) with a non-chromic chemical conversion treatment agent (Alsurf 501M (manufactured by Nippon Paint Co., Ltd.), 1% by weight). After the chemical conversion treatment, immersion water washing was performed in two steps, and then immersion treatment with pure water was performed. Thereafter, it was dried with hot air at 120 ° C. for 10 minutes and then naturally cooled.

  Electrostatic powder coating is carried out with a polyester-based powder coating (Bilusia PL2000 Gray PR, manufactured by Nippon Paint Co., Ltd.), and the coating thickness (100 μm) is obtained by heating and drying at 160 ° C. for 20 minutes (the coating object holding time). A primer coating film was obtained.

  An acrylic solvent-type paint (Superlac 5000AS70 11SV-14, manufactured by Nippon Paint Co., Ltd.) was applied to a dry film thickness of 20 μm, set for 10 minutes, and then heated at 140 ° C. for 10 minutes. Next, an acrylic solvent paint (Superlac 5000AW-10, manufactured by Nippon Paint Co., Ltd.) was applied to a dry film thickness of 40 μm, set for 10 minutes, and then heated at 140 ° C. for 20 minutes to form a multilayer coating film. Produced.

  Coating quality evaluation was performed by the above evaluation method using a cut surface of the design surface (spoke part) of the obtained coated aluminum wheel.

  As a result, as shown in Table 2, the impact test result was ◯, the SST test result was ◯, the CASS test result was ◯, and the yarn rust resistance test result was ◯.

[Example 2: Production of painted aluminum wheel]
As a chemical treatment, a coating pretreatment was performed in the same manner as in Example 1 except that an acid etching treatment was performed, and then the coating was performed. In the acid etching treatment, an acid etching agent (NP cleaner 208 (manufactured by Nippon Paint Co., Ltd.)) was sprayed at 2% by weight at 50 ° C. for 5 minutes. Then, immersion water washing was implemented in two steps. As a result of measuring the weight loss before and after the acid etching treatment with a test piece for measuring the elution amount, the elution amount was 5 g / m ² . Table 2 shows the measurement results of Fe residual amount, release agent residual amount, metal impurity amount, and impact test, SST test, CASS test, and yarn rust resistance test.

[Example 3: Production of painted aluminum wheel]
A pre-coating treatment was carried out in the same manner as in Example 1 except that no chemical treatment was carried out. The results are shown in Table 2.

[Example 4: Production of painted aluminum wheel]
A coating pretreatment was performed in the same manner as in Example 1 except that shot blasting was not performed, and then coating was performed. The results are shown in Table 2.

[Example 5: Production of painted aluminum wheel]
A coating pretreatment was carried out in the same manner as in Example 2 except that the shot blasting treatment was not carried out, followed by painting. The results are shown in Table 2.

[Example 6: Production of painted aluminum wheel]
A coating pretreatment was performed in the same manner as in Example 3 except that shot blasting was not performed, and then coating was performed. The results are shown in Table 2.

[Example 7: Production of painted aluminum wheel]
As a physical treatment, a pre-coating treatment was carried out in the same manner as in Example 1 except that barrel processing was not carried out, followed by painting. The results are shown in Table 2.

[Example 8: Production of painted aluminum wheel]
As a chemical treatment, an alkali etching treatment (50 ° C., 2 minutes treatment) with an alkali etching agent (Surf Cleaner SE300 (manufactured by Nippon Paint Co., Ltd.), 5% by weight) is performed, and an elution amount of 20 g / m ² is obtained. A coating pretreatment was carried out in the same manner as in Example 7 except that the coating was carried out, followed by coating. The results are shown in Table 2.

[Example 9: Production of painted aluminum wheel]
A coating pretreatment and then a coating were carried out in the same manner as in Example 2 except that barrel processing was not performed as a physical treatment. The results are shown in Table 2.

[Example 10: Production of painted aluminum wheel]
A coating pretreatment and then a coating were carried out in the same manner as in Example 4 except that barrel processing was not performed as a physical treatment. The results are shown in Table 2.

[Example 11: Production of painted aluminum wheel]
As a chemical treatment, a pre-coating treatment was carried out in the same manner as in Example 10 except that the alkali etching treatment of Example 8 was carried out, followed by painting. The results are shown in Table 2.

[Example 12: Production of painted aluminum wheel]
The coating was pretreated and then painted in the same manner as in Example 5 except that barrel processing was not performed as a physical treatment. The results are shown in Table 2.

[Example 13: Production of painted aluminum wheel]
The molten aluminum alloy (AC4CH) is cast into an automotive wheel mold coated with a commercially available kaolin / calcium salt mold release agent, and after cooling, the cast wheel taken out from the mold is used. The coating was pretreated by the method described above, followed by painting. The results are shown in Table 2.

[Example 14: Production of painted aluminum wheel]
A pre-coating treatment was carried out in the same manner as in Example 13 except that no chemical treatment was carried out, followed by painting. The results are shown in Table 2.

[Example 15: Production of painted aluminum wheel]
A coating pretreatment and then a coating were performed in the same manner as in Example 13 except that the shot blasting was not performed. The results are shown in Table 2.

[Example 16: Production of painted aluminum wheel]
A coating pretreatment and then a coating were carried out in the same manner as in Example 14 except that the shot blasting was not performed. The results are shown in Table 2.

[Example 17: Production of painted aluminum wheel]
As a physical treatment, instead of barrel processing, the brush polishing machine shown in FIG. 3 is used, and a silicate carbide containing nylon brush is used to perform forward polishing and reverse rotation for 20 seconds each. Was pre-painted in the same manner as in Example 16, and then painted. The results are shown in Table 2.

[Example 18: Production of painted aluminum wheel]
As a physical treatment, a pre-painting treatment and then painting were carried out in the same manner as in Example 16 except that instead of barrel processing, high-pressure water washing at 200 Mpa was carried out. The results are shown in Table 2.

[Example 19: Production of painted aluminum wheel]
As a physical treatment, a pre-coating treatment was carried out in the same manner as in Example 13 except that barrel processing was not carried out, followed by painting. The results are shown in Table 2.

[Example 20: Production of painted aluminum wheel]
As a physical treatment, a pre-coating treatment was carried out in the same manner as in Example 14 except that barreling was not carried out, followed by painting. The results are shown in Table 2.

[Example 21: Production of painted aluminum wheel]
A coating pretreatment and then a coating were carried out in the same manner as in Example 19 except that the shot blasting was not performed. The results are shown in Table 2.

[Example 22: Production of painted aluminum wheel]
As a chemical treatment, a pre-coating treatment was carried out in the same manner as in Example 21, except that the alkali etching treatment of Example 8 was carried out, followed by painting. The results are shown in Table 2.

[Example 23: Production of painted aluminum wheel]
As a chemical treatment, a pre-coating treatment was performed in the same manner as in Example 21 except that the acid etching treatment of Example 2 was performed, and then painting was performed. The results are shown in Table 2.

[Comparative Example 1: Production of painted aluminum wheel]
As a physical treatment, a pre-coating treatment was carried out in the same manner as in Example 16 except that barreling was not carried out, followed by painting. The results are shown in Table 2.

[Comparative Example 2: Production of painted aluminum wheel]
The molten aluminum alloy (AC4CH) is cast into an automobile wheel mold to which a release agent is not applied, and after cooling, the cast wheel taken out from the mold is used as the pickling treatment liquid. It was pre-painted and then painted in the same manner as in Comparative Example 1 except that it was pickled with the treatment liquid 1 (treated at 50 ° C. × 3 minutes) and washed with immersion water in two stages after the treatment. The results are shown in Table 2.

[Reference Example 1: Production of painted aluminum wheels]
Pre-paint treatment in the same manner as in Comparative Example 1 except that the molten aluminum alloy (AC4CH) is cast into an automobile wheel mold not coated with a release agent, and after cooling, the cast wheel taken out from the mold is used. And then painted. The results are shown in Table 2.

* 1: “Alkali a” has an etching amount of 5 g / m ² , “Alkaline b” has an etching amount of 20 g / m ² , and “Acid” has an etching amount of 5 g / m ² .

  As shown in Reference Example 1, only the pickling step (hereinafter referred to as “pickling step according to the present invention”) in the production method of the present invention for an aluminum wheel having no release agent remaining on the surface. If it carries out, the aluminum wheel excellent in paint adhesion and paint corrosion resistance will be obtained.

  In addition, as shown in the comparative example 2, when only the pickling process which does not satisfy the requirements in the manufacturing method of the present invention is performed on the aluminum wheel having no release agent remaining on the surface, the obtained aluminum wheel is obtained. Coating adhesion and coating corrosion resistance are poor.

  When a kaolin release agent is used as the release agent, the release agent remains on the aluminum wheel surface. For this reason, even if only the pickling process according to the present invention is performed on the aluminum wheel in which the release agent remains, as is apparent from Comparative Example 1, the coating adhesion and coating corrosion resistance of the obtained aluminum wheel are poor. .

  On the other hand, as shown in Examples 13 to 23, when manufactured by the method of the present invention in which the physical treatment and / or chemical treatment for removing the release agent and the pickling process according to the present invention are combined. Even when a kaolin release agent is used, an aluminum wheel excellent in coating adhesion and coating corrosion resistance can be obtained. In this case, even if the shot blasting process is performed as a physical process, an aluminum wheel excellent in coating adhesion and coating corrosion resistance can be obtained by performing the chemical process.

  When a graphite release agent is used as the release agent, a large amount of the release agent remains on the aluminum wheel surface. Even in such a case, as shown in Examples 1 to 12, an aluminum wheel excellent in coating adhesion and coating corrosion resistance can be obtained. In particular, as shown in Examples 1, 2, 4 and 5, by combining both physical treatment and chemical treatment, an aluminum wheel superior in coating adhesion and coating corrosion resistance can be obtained.

  Further, as shown in Examples 8, 9, 11, and 12, physical treatment is performed by combining a predetermined chemical treatment with the pickling treatment, even when a graphite mold release agent is used. Therefore, it is possible to obtain an aluminum wheel having excellent coating adhesion and coating corrosion resistance.

  As described above, in the present invention, the surface of an aluminum wheel is treated with physical means and / or chemical means and then washed with an acidic solution having a specific composition. The adhesion between the aluminum wheel and the coating film and the corrosion resistance of the coated substrate can be improved. Therefore, the present invention can be used not only in the field of manufacturing aluminum wheels, but also in a wide range of fields such as the automobile industry that uses aluminum wheels.

FIG. 1 is a diagram showing how an oxide film layer on the surface of an aluminum wheel changes in the method for manufacturing an aluminum wheel according to the present invention. FIG. 2 is a cross-sectional view showing a schematic configuration of an example of a barrel polishing apparatus that can be used in the method for manufacturing an aluminum wheel according to the present embodiment. FIG. 3 is a cross-sectional view showing a schematic configuration of an example of a brush polishing apparatus that can be used in the method for manufacturing an aluminum wheel according to the present embodiment. FIG. 4 is a cross-sectional view showing a schematic configuration of another example of a brush polishing apparatus that can be used in the method for manufacturing an aluminum wheel according to the present embodiment.

Claims (12)

A mold release agent removing step for removing the mold release agent by physical means and / or chemical means from the surface of an aluminum wheel formed by molding an aluminum base material or an aluminum alloy base;
After the release agent removing step, including a pickling step of washing with an acidic solution containing 0.5 g / L or more and 10 g / L or less of metal ions and 10 g / L or more and 100 g / L or less of nitric acid,
The metal ion in the pickling step includes at least one metal ion selected from the group consisting of Fe ³⁺ ion, Ni ²⁺ ion, Co ²⁺ ion, Mo ⁶⁺ ion, and Ce ⁴⁺ ion. A manufacturing method of aluminum wheels.   2. The method for producing an aluminum wheel according to claim 1, wherein the acidic solution further contains sulfuric acid of more than 0 g / L and 50 g / L or less.   The method for producing an aluminum wheel according to claim 2, wherein the acid solution has a weight ratio of sulfuric acid to nitric acid of less than 1/3.   The mold release agent is removed by at least one physical means selected from the group consisting of barrel polishing, brush polishing, buffing, and high-pressure water washing in the mold release agent removing step. The manufacturing method of the aluminum wheel of any one of these.   In the said mold release agent removal process, after processing by a shot blast as a physical means, it processes by a chemical means, The manufacturing method of the aluminum wheel of any one of Claims 1-3 characterized by the above-mentioned.   The method for producing an aluminum wheel according to any one of claims 1 to 5, wherein the chemical means is chemical etching using an alkali treatment liquid or an acid treatment liquid. The chemical etching method for aluminum wheels according to any one of claims 1 to 6, characterized in that 40000mg / ^{m 2} or less etched 1000 mg / ^{m 2} or more of the surface of the aluminum wheel. In the surface of the aluminum wheel after the pickling step,
The weight ratio of copper to aluminum (Cu / Al) is 0.1 or less,
The weight ratio of iron to aluminum (Fe / Al) is 0.1 or less,
The weight ratio (Ni / Al) of nickel and aluminum is 0.1 or less, The manufacturing method of the aluminum wheel of any one of Claims 1-7 characterized by the above-mentioned.   The method for producing an aluminum wheel according to any one of claims 1 to 8, further comprising a chemical conversion treatment step of chemical conversion treatment of the surface of the aluminum wheel after the pickling step.   The method for producing an aluminum wheel according to claim 9, further comprising a coating step of coating the surface of the aluminum wheel after the chemical conversion treatment step.   The method for manufacturing an aluminum wheel according to claim 10, wherein the coating is powder coating.   The aluminum wheel manufactured using the manufacturing method of the aluminum wheel of Claim 10 or 11.

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